Lodgepole pine forests in parts of Wyoming and other areas of the Intermountain West are being infested by the native mountain pine beetle – a voracious bug smaller than your little fingernail that is thriving in a warming climate.

Triggered by a “perfect storm” of extended droughts, warm winters, and old, dense forests, mountain pine beetle populations have exploded across a landscape of lodgepole pine trees throughout Colorado and southeastern Wyoming.

The mountain pine beetle is a true predator on many western pine trees because to successfully reproduce, the beetles must kill host trees. They typically kill trees already weakened by disease or old age, but even a healthy tree’s defensive mechanisms can be exhausted when beetle numbers are at epidemic levels. The beetle attacks pines in late summer, dispersing a chemical signal that attracts other beetles to mass-attack the tree. When the beetles bore through the bark of the tree, they introduce blue-stain fungus, which can work quickly to kill the tree. Trees stressed by drought and old-age are unable to produce sufficient defenses to fend off beetle attacks. The beetles form tunnels and lay eggs underneath the bark, which hatch into larvae. The larvae spend the winter underneath the bark and emerge as adults in the summer, beginning the cycle again.

The U.S. Forest Service estimates that by 2012, the majority of lodgepole pines in northern Colorado and southern Wyoming will be killed by the beetle. Currently, there are four million acres of lodgepole pine trees on Forest Service land affected by mountain pine beetle infestation. Extensive beetle kill has resulted in ecosystem-wide impacts such as increased potential for wildfires and some loss of other tree species such as Douglas fir.

The research team of students and staff is led by Anna D. Chalfoun, Ph.D.,with the Cooperative Unit. Chalfoun said the research aims to determine which alternative stand types (for example, young previously harvested lodgepole and/or spruce-fir) may best support wildlife species until lodgepole stands can regenerate after the ongoing infestation.

The lodgepole pines are not the only trees favored by the mountain pine beetle. The Fish and Wildlife Service is currently working on a listing determination for the entire range of whitebark pine, another western pine tree species heavily impacted by the insects.

“Because of warming temperatures, scientists are now seeing significant beetle impacts even in the high elevation sites occupied by whitebark pine,” said Amy Nicholas, a Service biologist in Rock Springs, Wyo. “These sites are usually quite cold and unfavorable for epidemic levels of mountain pine beetle. That no longer seems to be the case.”

The Service anticipates completing its review, which will determine whether the whitebark pine will become a candidate for ESA listing, in mid-July, Nicholas said.

About the series – The Clime of Conservation in America: 50 Stories in 50 States

The U.S. Fish and Wildlife Service and its partners have launched an unprecedented series of 50 stories for 50 consecutive weekdays that explores the many ways accelerating climate change is impacting or may impact fish and wildlife across America.

In keeping with the 2011 Earth Day theme of “A Billion Acts of Green,” the series will cover 50 states, examining regional challenges posed by climate change. They also will highlight science-based solutions and collaborative actions that are making a difference for wild things and wild places.

Since the series started on Earth Day, April 22, the Service has published 14 stories covering a broad range of issues and impacts from the states of South Carolina, Massachusetts, Missouri, Louisiana, Idaho, California, Arizona, Delaware, Montana, North Carolina, Wisconsin, New Mexico, Ohio and Kentucky.